This is an example original site, where the announcement setting is disabled. 

In the admin portal we are able to enable the announcement feature and add a few settings.

The "Message" option is the text that will be shown inside the banner.

The "Link url" is the link to the page WITHIN the portal. Notice in the image below I have "courses", this will take the user who clicked the text to -> https://course-dev.skills.network/courses, this can be used to link into specific courses or such.
The text color and background color are the colors chosen for the text and background of the banner.

The "Position" can either be at the top of the page or the bottom of the page and will stay there until closed or moved away into a course.

The "Visibility" can be set to Public meaning anyone that goes onto the portal REGISTERED or NOT can see the banner. If set to Private, only logged in users can see it.

Once all the settings have been chosen, click on the "Update Settings" button to save it.